U-shaped semiconductor structure

1. A method for forming a U-shaped semiconductor device, comprising: growing a U-shaped semiconductor material along sidewalls and bottoms of trenches, the trenches being formed in a crystalline layer; anchoring the U-shaped semiconductor material and removing the crystalline layer; backfilling underneath the U-shaped semiconductor material with a dielectric material for support; and forming a semiconductor device with the U-shaped semiconductor material.

2. The method as recited in claim 1 , further comprising growing the crystalline layer on a monocrystalline substrate.

3. The method as recited in claim 2 , wherein the trenches are formed in the crystalline layer by patterning a hard mask and etching the trenches using a reactive ion etch process.

4. The method as recited in claim 1 , wherein the U-shaped semiconductor material includes upright portions and a lateral portion, and the method further comprises forming spacers on the upright portions and etching the lateral portion to reduce a thickness of the lateral portion.

5. The method as recited in claim 4 , wherein etching the lateral portion includes reducing the thickness to about one half that of an upright portion.

6. The method as recited in claim 1 , wherein anchoring the U-shaped semiconductor material includes forming structures at end portions of the U-shaped semiconductor material such that when the crystalline layer is removed a cavity is formed between the U-shaped semiconductor material and an underlying substrate.

7. The method as recited in claim 1 , wherein forming the semiconductor device with the U-shaped semiconductor material includes forming a fin field effect transistor wherein a channel is formed through the U-shaped semiconductor material.

8. A method for forming a transistor with a U-shaped channel, comprising: epitaxially growing a U-shaped semiconductor material along sidewalls and bottoms of trenches to form U-shaped fins, the trenches being formed in a crystalline layer; anchoring the U-shaped fins and selectively removing the crystalline layer; supporting the U-shaped fins by backfilling underneath the U-shaped fins with a dielectric material; forming a gate dielectric and a gate structure transversely over a longitudinal direction of the U-shaped fins; and forming source and drain regions adjacent to spacers formed parallel to the gate structure.

9. The method as recited in claim 8 , wherein the crystalline layer is formed on a monocrystalline Si substrate and includes SiGe; and epitaxially growing a U-shaped semiconductor material along sidewalls and bottoms of the trenches includes growing Si.

10. The method as recited in claim 8 , wherein the trenches are formed in the crystalline layer by patterning a hard mask and etching the trenches using a reactive ion etch process.

11. The method as recited in claim 8 , wherein the U-shaped fins include upright portions and a lateral portion, and the method further comprises forming spacers on the upright portions and etching the lateral portion to reduce a thickness of the lateral portion.

12. The method as recited in claim 11 , wherein etching the lateral portion includes reducing the thickness to about one half that of an upright portion.

13. The method as recited in claim 8 , wherein anchoring the U-shaped fins includes forming structures at end portions of the U-shaped fins such that when the crystalline layer is removed a cavity is formed between the U-shaped fin and an underlying substrate.

14. The method as recited in claim 8 , wherein the U-shaped fins form a fin field effect transistor wherein a channel is formed through the U-shaped semiconductor material.